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(11) | EP 1 675 004 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Fault tolerant system and controller, access control method, and control program used in the fault tolerant system |
| (57) The present invention has been made to realize access processing performed in accordance
with synchronous/asynchronous state between processors in a fault tolerant system.
In two systems that constitute a fault tolerant system, a router assigns, to an access
packet transmitted from a CPU to an 10 device, tag information including ID codes
of access source and destination and information indicating whether the access packet
is synchronous access. An access comparison section has buffers and that retain the
packets from the CPU on a system basis, a tag check section that determines whether
each packet is synchronous packet access based on the tag information assigned to
the packets retained in the buffers, and a comparison section that outputs the packet
from one system to an IO IF and discards the packet from other system in the case
where the packet is synchronous access.
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